Dear Sunijapur,
Apparently, your question is not clear to me. What you mean by " F&F settlement " and the correlation of the " NOC " you mentioned to it when the employee comes back after his long absence are also equally confusing a person like me who never worked in any industrial establishment belonging to Private Sector or Public Sector.
Well, unauthorised absence from duty for short or longer duration, apart from being a misconduct, is a breach of the contract of employment on the part of the employee and the immediate consequence is proportionate loss in his wages. When such absence is for a very long period, it has to be treated as abandonment of services and disciplinary action has to be taken against the absentee and it can end up with dismissal from service or under humanitarian considerations, he can be permitted to resign so as to facilitate his future employment elsewhere. Only then the question of F&F Settlement will arise. In the event of continued abscondence on the part of the employee at every stage of the procedure described above, you have to calculate the pending dues if any from your own records and after deducting any sums due to the management, you have to deposit the amount with the State Labor Welfare Fund under the unclaimed amounts deposit head as rightly observed by our friend KK!HR. In respect of the statutory gratuity,if any, you have to deposit the sum with the Controlling Authority for the area under the Payment of Gratuity Act,1972.